1. Field of the Invention
This invention relates in general to vibrational energy isolators, and in particular, wire rope isolators. More specifically, but without restriction to the particular embodiment hereinafter described in accordance with the best mode of practice, this invention relates to wire rope vibration isolators employing a plurality of U-shaped half loops in a wire rope or a number of wire ropes that flex during use so as to dispel vibrational energy.
2. Background of the Prior Art
Excessive vibrational energy can damage and/or cause the deterioration of sophisticated machinery. In industries in which movement is inherent in daily operations, such as avionics and shipping, the need to minimize unwanted vibrational energy is imperative. These industries have come to rely heavily on sensitive electronic equipment, like navigational computers, to maintain daily operations. Constant jostling of electronic equipment can cause system failures that lead to costly downtime to replace and/or repair the damaged equipment.
Over the years, many devices have been designed to contain damaging vibrations and dampen unwanted kinetic energy. These devices use the unwanted kinetic energy to move simple machinery, like pistons and springs, so as to divert the unwanted energy from shock-sensitive equipment attached to the isolator. A good example of a member of this class of devices is the wire rope isolator. The most common wire rope isolators employ a helical wire cable secured between a pair of retaining members. When the isolator is in use, vibrational energy causes the wire rope coil to move in a spring-like fashion, which in turn moves the retaining members vertically toward each other. This movement drains the vibrational energy before it reaches the affixed sensitive equipment.
The art of wire rope vibration isolators has been contributed to by a number of proposed devices detailed in U.S. Pat. No. 5,549,285 issued to Collins and U.S. Pat. Nos. 5,441,243 and 5,791,636 both issued to Loziuk. These patents describe vibrational energy isolators that consist of coiled wire ropes secured between two parallel retaining bars. Holes drilled into the retaining bars maintain the helical shape of the wire rope. Vibrational energy causes the wire rope coil to contract which in turn moves the entrapment bars vertically relative to each other thus absorbing vibrational energy in the process.
There are several drawbacks, however, with the helical design. First, conventional isolators are ineffective when the support load is a few pounds. Further, because helical wire rope isolators are intended to support heavier loads, the components of these isolators are manufactured from stronger more solid materials like steel which tends to be more costly than less sturdier metals like aluminum. In addition, the assembly of wire rope isolators requires a tool to wind the wire rope and the another to secure the wire coil by either fastening or crimping. This factor, coupled with the need to use more expensive materials, increases the costs associated with the production of helical wire rope isolators. Finally, in addition to aforementioned limitations, helical wire rope isolators are also not well suited for applications with limited spatial requirements due to the requirement that the wire coil be of a certain length to be functional.
A type of wire rope isolator not employing a wire rope coil is described in French Patent No. 2,601,739 issued to Le Derf et al. This wire rope isolator consists of a pair of entrapment bars in which a singular wire rope is manipulated into a "saddle" formation. Two pairs of parallel U-shaped half loops are formed that are parallel to the axis of one of the retaining bars. When in use, the U-shaped half loops flex and contract causing the retaining bars to move vertically relative to each other. This design, however, can lack uniform stiffness on all axes.
Accordingly, there continues to be a need for wire rope isolators that can support relatively light loads, are constructed from less costly materials, require limited steps in manufacturing, can be used when space is limited and provide uniform stiffness about all axes of the isolator.